Crystal elements are used as mirrors in high-energy lasers, space technology and synchrotrons. In these applications, intense thermal energy (up to 100 kilowatts) is produced that creates bumps in the surface of the mirror, limiting instrument performance. This optical distortion can be lessened by improving heat transfer and/or lowering coolant temperature and using materials that perform well at low temperatures. The best results are obtained by applying both techniques.
Current designs use water-cooled micro-channels or etched channel wafers bonded together to create multi-stack, multi-hole geometries for the optical substrates. The working surface is either bonded to the substrate or created separately by one of several deposition techniques. But as the coolant is pumped through the cooling channels at very high velocities for high heat transfer, it causes "jitters". Although vibration is undesirable, the resulting level of mirror performance is adequate for many applications. However, where very critical optical distortion tolerances are involved (less than 3 .ANG./W/cm.sup.2), water cooling is not satisfactory.
Ammonia and other cryogen coolants have been suggested, but the geometries of prior art optics do not support the low boiling heat flux of these coolants in the preferred single-phase mode.
It is therefore a primary object of this invention to provide a method for constructing and operating a cooled optic which optimizes performance by exploiting a coolant which remains single phase and has superior heat transfer capacity at operating temperatures.
In the accomplishment of the foregoing object, it is another important object of this invention to provide a method for constructing a cooled optic which maximizes heat transfer area by incorporating porous materials with unusually high thermal conductivities.
It is a further object of this invention to present a method for constructing a cooled optic which is inexpensive, requiring limited machining and using commercially available components.
It is another important object of this invention to provide a method for operating a cooled optic which results in very small temperature differentials and hence negligible thermal stresses and optical distortion of the crystal.
A yet further object of the present invention is to present a method for operating a cooled optic which is predictable, stable, and vibration free, while meeting high optical performance requirements.
Additional objects, advantages and novel features of the invention will become apparent to those skilled in the art upon examination of the following and by practice of the invention.